Telemetric controller



' Nov. 4, 1941'. as. SMITH, JR 2,261,300

TELEMETRI C CONTROLLER Filed Dec. 18, 1937 2 Sheets-Sheet l Ed 5. SmithJn I INVENTOR ATTORNEY Nov. 4, 1941. E. 5; SMITH, JR

TELEMETRIC CONTROLLER Filed Dec. 18, 193'? 2 Sheets-Sheet 2 INVENTOR ATTORNEY Patented Nov. 4, 1941 TELEMETRIG CONTROLLER Ed s. Smith, In, St. Albans, N. Y., assignor to Builders Iron Foundry, Providenca-R. 1., a corporation of Rhode Island Application December 18, 1937, Serial No. 180,486

Claims.

This invention relates to methods of and apparatus for telemetrically controlling a variable quantity. w

Afeature oi the invention resides in the transmission of signals corresponding with the values of a physical condition, such, for example, as the diiierential pressure produced by a flow of liquid in a conduit, and controlling a motor in accordance with the departure from equality of the oscillations of a member controlled by said sigtion of motion in immediate response to the apj propriate telemetric signals. Combined with said pilot means is a more powerful regulating means which is brought into action only when necessary to eifect the desired regulation.

A further object of the invention resides in the provision of a control system wherein the pilot means, while capable of sensitive and prompt response to very small variations from" the set value of a variable, will not cause fluctuation or hunting. The pilot means at the same time is capable of acting as an integrator, bringing the control-effecting means into action promptly upon the accumulation of a predetermined variation from the set value.

All of the foregoing objects moreover are at-' tained with only two wires, or with on wire and ground, between the quantity-responsive signal transmitting means and the pilot means.

Other objects and advantages of the invention I will be hereinafter described and claimed.

In the accompanying drawings:

Fig. 1 is a diagrammatic view, with certain parts in elevation and others in vertical section, illustrating an mbodiment 'of my invention.

Fig. 2 is a view in side elevation. partly in secmotor may, for example, include a pair of field interposed in the conduit is an orifice plate 2, manually adjustable vertically to vary the area of the orific 2' through which the liquid flows. Taps 3 and 4 from conduit l are connected to a conventional U-tube 5 containing a manometric liquid such asmercury, the high pressure tap 3 being connected to leg 6 of said U-tube, and the low pressure tap 4 to leg 1. A float 8 rests upon the surface of the manometric lipuid and is thus positioned in accordance with the differential pressure between taps 3 and 4, or; in other words, in correspondence with the square of the velocity of the liquid flowing in the conduit i.

The stem. 9 of float 8 carries a contactor Hi which engages a square root cam H, rotated at constant speed by synchronous motor 12, through suitable gearing l3. 'Motor I2 is energized from alternating current supply lines l4, l5. Due to the shape of cam II, the period of engagement between said cam and the contactor Ill in each cycle of rotation of said cam is proportional to the square root of the difierential pressure between points 3 and 4 and is thus proportional to the velocity of the liquid flowing in the conduit I.

Positioned in conduit I downstream with respect to tap 4 is a valve i6 for regulating the velocity of fiow of the liquid in said conduit. This valve is operable in either direction by a reversible motor ll of any suitable type. Said windings for causing operation of its armature in opposite directions, respectively; one of said windings being connected by 'a wire l8 with a contact l9, and the other of said windings being connected by a wire with a contact 2|, both windings being furthermore connected by a common return wire 22 with main supply wire 14. Motor shaft '23 may be screw threaded as shown and engage a nut 24, connected by 'pin 25 and slot 26 with an arm 21 extending from and secured to the pivot shaft 28 of the valve IS. The latter is here illustrated as of the butterfly type.

Movable in the gap between contacts 49 and 2| are contacts 29 and- 30, carried by a resilient blade 3|, adapted to engage the respective contacts l9 and 2| upon movement of the blade 3| through a suflicient extent in the proper direction. Said blade 3| is mounted on an arm 32, which has journaled thereon a pinion 33 meshing with a pair of diiferential gears 34,35. Said arm 3| acts as the conventional spider element of the diiferential gear system 33, 34, 35, and

turns about the axis of said gears 34 and 35 whenever said gears move unequally.

A wire 22 connects contacts 29 and 30 to main line wire l5.

Gear 34 is connected, through a conventional friction coupling'36, with the shaft of motor ll, while gear 35 is driven by a pilot motor 31, through pinion 38 on the shaft of said motor, gear 39, and shaft 40, In the embodiment shown in Fig. 1 it will be understood that the shaft 40 and the shaft of the motor i! are in line with each other and that the axes of rotation of gears 34 and 35 are the axes of rotation of said shafts, though said gears are illustrated at an angle to said shafts to show the differential mechanism more clearly.

Motor 37 is of a well known type comprising a field coil 4|, which is continuously connected to the alternating current supply lines l4, l5, and further comprising a pair of shading coils 42, 43, A circuit through coil 42 is continuously closed through a resistance 44 in series with said coil as shown. Coil 43 is connected through wires 45 and 48 with contactor l0 and cam I respectively, so that a low resistance circuit through said coil 43 is closed whenever said contactor is engaged with said cam and is broken whenever said concoil 43 is open the pilot motor 3'! will run steadily u in one direction, and as long as said circuit is closed said motor will run steadily in the opposite direction. While in the present example of the invention the resistance in series with coil 42 is so chosen that the forward and reverse speeds are equal, it will be understood that, if desired, said resistance may be varied, through the manually adjustable contactor 48, to vary the ratio between the forward and reverse speeds to the extent desired.

The operation of the embodiment illustrated in Fig. l is as follows:

The orifice 2' creates a differential pressure between the points 3 and 4 which varies as the square of the velocity of the liquid flowing in the conduit So long as this differential pressure is at such value that the circuit through coil 43 is closed by the engagement of contactor l0 and cam H in each cycle for a period equal to the period in the cycle in which the cam H and contactor H] are disengaged, the pilot motor 31 operates the arm 32 through equal extents in opposite directions in each cycle. In other words, as long as the value of the differential pressure is such that the respective periods of energization and de-energization of coil 43 in each cycle are equal, arm 32 simply oscillates through equal extents, and without engaging either contact 29 or 30 with its associated contact l9 or 2|, Motor I1 remains out of action as long as this condition continues.

If the differential pressure is, for any reason, such as increased flow, greater than that above referred to, the coil 43 is energized for a longer period than is coil 42, and consequently the arm 32 is operated through a greater extent in one direction than the other, said arm moving further toward that one of the contacts l9, 2|, which when engaged by the corresponding contact on arm 32, will cause motor I! to operate valve IS in the direction for decreasing the flow in conduit thereby re-establishing the desired differential pressure. As soon as motor I"! commences operating, gear 34 is turned thereby in such direction as to move arm 32 to disengage said contacts, and upon such disengagement the motor I! is de-energized. Said contacts are disengaged by rotation of gear 34 when motor 3! ceases rotating gear 35 in the direction for engaging said contacts. The foregoing action may be suflicient to bring valve I6 into the proper position for obtaining the appropriate differential pressure, but, if it is not, said action is repeated in one or more successive cycles, the pilot motor 31 effecting engagement of the contacts aforesaid and the valve motor |l disengaging said contacts, until valve l6 assumes the proper position. Similarly, if the differential pressure is at a value lower than that requisite for the energization of coils 42 and 43 for equal periods, arm 32 is turned further in the direction for bringing the proper contacts into engagement for causing motor I! to operate valve IS in the opening direction, and said motor actuates said valve in said direction until said contacts are disengaged, this action being repeated in each cycle, if necessary, until valve I6 is positioned to produce the appropriate higher differential pressure,

With valve l6 set in the position corresponding to the differential pressure aforesaid, any variation of said differential pressure will result in operation of arm 32 through a greater extent in one direction than in the other, bringing one of its contacts further toward the appropriate contact 9 or 2|, for causing motor I! to turn valve |6 in the proper direction to restore said differential pressure to the set value. By suitably spacing the contacts l9, 2| from the corresponding contacts 29, 30 on the arm 32, the latter may be permitted to move a finite distance in either direction, within the space between said contacts |9, 2|, without causing operation of the valve motor H, but upon accumulation of sufficient variations in one direction or the other said motor operates to shift valve IS in the direction for restoring said differential pressure to within the range of permissible departure. The motor 31 and associated contact mechanism thus function as a form of integrator.

The velocity of flow of the liquid in conduit I, as above noted, is a function of the differential pressure between points 3 and 4, said velocity varying as the square root of said differential pressure. The quantity rate of flow of said liquid equals the product of its "elocity times the area of the orifice 2. It will hence be apparent that the mechanism above described enables a desired quantity rate of flow (hereinafter referred to simply as rate of flow) to be accurately maintained for a given setting of the orifice plate 2, Whenever a change in said rate of fiow is de-- sired, the operator simply raises or lowers the orifice plate 2 by turning the knob 49. A scale 49 may be associated with said knob as shown. Upon thus changing the position of the orifice plate 2 the differential pressure between points 3 and 4 is changed for only a short interval, and is restored to its former value by the operation of the valve motor under control of the pilot motor 31 in the manner above described.

It will thus be seen that through the apparatus above described, departures from a given differential pressure are automatically rectified with promptness and precision and a given differential pressure effectively maintained. To vary the flow rate it is merely necessary for the operator to change the setting of the orifice plate 2; the pilot motor 31 controlling the valve motor IT to maintain the differential pressure at a given value despite adjustments of said plate so that the flow rate varies in proportion to the position of said plate. And as long as the plate 2 is set in a given position, the apparatus above described speedily corrects any departures of the diiferen tial pressure from such value as maintains the contacts 29, 30 out of engagement with contacts it, ill, and rapidly and accurately restores said differential pressure to said value. Thereby the rate of flow, which as above noted is commensurate with the differential pressure, is effectively maintained. at a given value. So long as the differential pressure remains at the desired value, within the limits, as-deterrnined by the spacing of the contacts ill, it, the valve remains at rest, with contacts 29 and oscillating within said space, but when the integrated departures :Erom said value exceed said limits, the contact carrying arm 32 establishes the necessary circuit to bring the valve motor ll promptly into action to restore the differential pressure within said limits. The latter may be narrowed as desired appropriate adjustment oi said contacts it) and 220.

An important feature of the invention resides in the fact that it provides uniform response to changes in the differential pressure. in other words, the length of time required to effect a given correction is constant. ifiincetlie apparatus maintains a uniform differential pressure,

regardless of the setting of the orifice plate, its

speed oi response to a change in said. diiferential pressure is uniform. it may further be noted that in the apparatus above described, the value of the differential pressure necessary to provide an on-signal of a duration equal to the oil-portion of the cycle is well above the values in the neighborhood of zero; so that the time of response to differential pressure changes is not only constant but is considerably shorter than for changes in differential pressure at values in the lower range. In short, by maintaining a uniform differential pressure at values substantially above the lower range, a marked uniformity and sensitivity of response of the transmitter comprising the contactor I0 and cam H, and hence of the means for operating the valve i6, is obtained. Since, as above noted, the duration of engagement between contactor i0 and cam l-l varies as the square root of the differential pressure, the changes in said duration corresponding to changes in said differential pressure, at the valuethereof requisite for maintaining coil 43 energized for 50% of each cycle, are substantially uniform. it may be further observed that the variation of flow rate with a given change or It niay also be noted that the type of motor I 31 illustrated is practically independent of inertia and is capable of instant response to the engagement and disengagement of cam Hand contactor i0. Tests have shown that such motor will reverse and come up to speed within a single alterhating current cycle, i. e., of a second with alternating current of 60 cycle frequency. at

the same time it will be understood that other forms of low inertia and high responsiveness can be utilized, such, for example, as the reversible motor shown at B0 in Fig. 3, and more particularly referred to hereinafter. It will also be evident that any suitable conventional type of motor may be employed for the valve motor ll. Mag= netie braking means well known in the art for preventing over travelof the motor may also be employed in connection with said motor it.

The speed of the valve motor and/or of allot motor Ell, may be varied in any welidmown manner so as to give maximum speed ct valve it without hunting under a variety of conditions. A conventional speed adjusting element is illustrated for this purpose at 58 in connection with the motor 3W.

it will further observed that, while the pilot motor may be of low inertia, instantly and cre cisely responsive even to minute variations. in the signals received from the transmitter, the valve motor it may be considerably more poweriul, to insure effective operation of the valve.

The valve motor at the same time is under the resiliency of the blade 3| 9. slightoperation oi motor 31 is permitted after engagement of either pair of contacts. If desired, a friction drive coupling similar to coupling .36; may be interposed between gear 35 and the pilot motor, enabling'slippage to occur whenever motor 31 is rotating and arm 32 is in either extreme position of its movement with blade 3| flexed.

it may be further observed that, with the connections illustrated between the valve l6 and differential gear 3|, the latter, and hence the contact arm 32, will be driven at a higher rate differential pressure at these values is less than for the same change in differential pressure at lower values, so that by operating the control apparatus at the higher values of the differential pressure the maintenance of uniform flow rate is facilitated.

Through the provision of the adjustable orifice plate 2, the sensitivity and iso-responsiveness of transmitter may beextended over a wide however, by the control of the transmitter signals over the valve it. Thus, a control over a broad range of variations in rates of flow is attainable with a given and effective differential pressure "value, and hence with constant sensitivity and responsiveness of the apparatus.

of speed from motor 11 than is valve i6, and also at a, higher speed than gear 35 is driven by pilot motor 31. This permits minute adjustments of the valve l6. Said connections may, or course, be varied as desired.

It may also be noted that with the apparatus above described any change in the duration of the signal resulting from engagement 01' contactor ill with cam H effects an increased change in the oscillation of the contact carrying arm 2. For example, with the signal duration 50% of the cycle, a 1% decrease in said duration changes the "on period to 49% and the "off period to 51%, giving a net change of.2% in the effect upon the oscillating contact carrying arm 82. The sensitivity of the apparatusis thus doubled.

The provision for effecting control through complemental cyclical "on-oflf" impulses further enables the provision of only two wires (or one wire and ground) between the transmitter and the control efl'ecting means. 1

r In Fig. 2 I have illustrated a. pair of magnetically operated enclosed mercury switches 50, f5!

of known type, for energizing the respective field coils of the valve motor I1 under control of arm 32' of the differential gearing. Each switch 50, 51 has a globule 52, 53, respectively, of mercury or other suitable conducting liquid, connected to wires I8, 20, from the coils of valve motor I1. The common return wire 22' is connected through branches 22" to movable magnetic elements 54, 55, in the respective switches. Differential gear arm 32 on which is journaled pinion 33 for meshing with gears 34, 35, is the same as arm 32 of Fig. 1 except that said arm 32' is shown rigid throughout its length and has affixed thereto a pair of permanent magnets 56, 51. Approach of either magnet to within a predetermined distance of the corresponding switch 50 or draws the magnetic element 54 or 55 of said switch into contact with the mercury globule 52 or 53, thereby energizing the corresponding coil of the valve motor I1. In Fig. 2, the element 55 of switch 5I is shown drawn into contact with globule 53 by magnet 51. While the magnetcarrying portion of arm 32' might be made resilient, the magnetic field of said magnets enables said arm to move slightly beyond the position in which it causes operation of either of the enclosed mercury switches.

In Fig. 3 the signals from the transmitter contactor I0 and cam II control not only a reversible pilot motor 60, but also an indicator BI and a recorder 62. As long as contactor I0 and cam II are in engagement in each cycle, an impulse is sent from main I4 through wire 63, through said contactor and cam, and thence through wire 84, relay coils 85, 66, and 81, and wire 68 to main I5.

The reversible synchronous motor 50 is of a type well known in the art and comprises a pair of coils 88, one of which, when energized, effects rotation of the motor in one direction, and the other of which, when energized, effects rotation of the motor in the opposite direction. Said coils are connected, respectively, to contacts 1 I, 12, and by a common return wire 13 to main I4. A contact blade 14 is connected to main I5 by wire 15 and maintained in engagement with contact 12 by spring 16 whenever coil 61 is deene'rgized, at which time a circuit is closed through coil 10 and the motor '80 runs in one direction. As soon, however, as coil 81 is energized, the circuit through motor coil 10 is broken and a circuit through motor coil 68 is established, whereupon said motor operates in the reverse direction. Motor 80 controls the valve motor I1 in the same way as does motor 31 of Figure 1, a pinion 38 being shown on the shaft of said motor 60 for meshing with gear 38 to drive gear 35 of the differential gear contact mechanism of Fig. 1. As in the case of motor 31, motor 60 operates in one direction for one-half of a cycle and in the opposite direction for the remaining half as long as the differential pressure is at the corresponding value, during which time the motor I1 is out of action; but upon the occurrence of an appreciable (or persistent) inequality of the off and on periods motor E1 is brought into action and operates valve I6 in the direction to restore equality between said off and on periods.

The indicator apparatus 6| located at a receiving station remote from the transmitter, is illustrated as comprising a reversible motor 18 of the same type as motor 31. Coil 18 of said motor is connected across the mains I4, I5, while a circuit through coil 80 is continuously closed through the adjustable resistance 8|. Coil 82 is connected to a pair of contacts 83, 84. Contact 84 is carried by a blade 85 which is biased by spring 86 to separate said contact from contact 8-3. These contacts are separated, and coil 82 open-circuited, as long as contactor I0 is out of engagement with cam I I, but when said contactor engages with said cam, coil 65 is energized as noted above, and thereupon attracts blade 85 which moves contact 84 into engagement with contact 83. On deenergization of coil 65, spring 86 retracts blade 85 and permits contact 84 to separate from contact 83. Thus it will be seen that motor 18 operates concurrently with motor 60 and oscillates the shaft 81 in each cycle through extents commensurate with the on" and off signal periods. An arm 88 on said shaft oscillates with the latter within the space provided by the extensions 88, of an arm 8I secured to shaft 82 which carries a pointer 83, cooperating with a scale 84. So long as the on and off signal periods are equal, the arm 88 oscillates without actuating the arm 8| and shaft 92, but upon an appreciable departure from equality of said periods said arm 88 operates said arm and shaft and thereby moves pointer 83 through an extent commensurate with the difference between said on and off periods. Pointer 83 thus stands still as long as the rate of flow remains at the value determined by the setting of the orifice plate, but said pointer is shifted in one direction or the other as soon as the actual ratedeparts from that set. Said pointer further indicates on the scale 84 the algebraic sum of the departures from the set rate and thus acts also as an integrator. The shaft 92 may also operate a conventional counter mechanism 85 to integrate said departures and exhibit the total thereof.

A brake shoe 86 carried by an arm 81 is constantly maintained by a spring 88 in engagement with a disk 89 on shaft 82, to insure retaining said shaft, and the pointer 83, in their set positions.

The recorder apparatus 82 includes a synchronous motor I00 connected by wires IOI, I02 to the mains I4, I 5, and rotating in unison with the transmitter motor I2. Said motor, through gearing I03, I04, continuously drives a shaft which has secured thereto two worm gears I05, I06, the threads of one of which run in the reverse direction from those of the other. Said worms mesh with worm wheels I01, I08, respectively, so that the latter are rotated continuously in opposite directions. A pair of electro-magnetic clutches (not shown, but which may be similar to those indicated at K1 and K2 in Wilde Patent No.

1,985,130) rotate with said worm wheels and are adapted when energized to clutch the respective gears I09, IIO to the rotating shafts of said worm wheels. Slip rings III and brushes II2 convey current to said electromagnetic clutches.

WiresII3, II4 run from brushes of the respective clutches to contacts H5, H6, respectively. A return wire H1 is connected to the remaining brushes of said clutches and to wire I5, as shown. Connected to wire I4 is a contact blade I I8 which is maintained in engagement with contact I I5, by spring II9, as long as contactor I0 at the transmitter is disengaged'from cam I I. At such times, the clutch which rotates with worm wheel I01 is energized, and gear I08 rotates with said worm wheel. When contactor I0 engages cam II, coil 68 is energized and attracts the blade H8 into engagement with contact H6. The clutch between gear I09 and worm wheel I01 is now deenergized, and the clutch between worm wheel I08 and gear H is energized. It will thus be apparent that the gears I09 and III) rotate in each cycle through extents commensurate with the respective "on and oiP' signal periods.

Gear I09 meshes with a gear I which in turn drives a gear :12 l on the shaft of which is an arm i22 having a portion bent laterally, as shown, to cooperate with a pointer I23 iournaled ior rotation about the axis of gear I2I. Similarly, gear 11 i0 meshes with a gear I24 which engages a gear i25 on the shaft of which, coaxial with that of gear i2i, is an arm I26 having a portion bent laterally to cooperate with said pointer. Weights 922, 628 attached to cords running over the hubs or" the respective gears I20, 'i2d, restore the latter, together with the respective arms H2, M6, to a normal position when the respective clutches arede-energized. In its initial or return position, each of said arms rests upon a suitable stop i29.

From theioregoing description, it will he seen that as soon as contactor Ifl engages cam i i, the gear lid is clutched to worm wheel Idil and the arm 52% is thereby rotated counter-clockwise (Fig. 3) from its initial position, said arm continuing to rotate counter-clockwise until said contactor ill becomes disengaged from said cam. Thereupon, gear iiil is unclutched from worm "wheel i 98, and weight I28 restores arm M6 to its initial position. As soon, however, as contactor it and cam it become disengaged, the clutch between gear 809 and worm wheel I01 is energized,

and cam again come into engagement. Thus the So long as said on periods equal the bfi periods, the arms I22 and I26 move through equal extents and do not affect the setting of pointer 923, which then remains undisturbed in the position shown, 1. e., at the zero position with respect to chart I30. However, upon departure of the flow rate from the set value, the resulting inequality of the on and oil" periods aforesaid causes unequal movements of the arms I22 and I28 with consequent shifting of pointer I23 through an extent commensurate with said departure and in the direction corresponding thereto. A friction shoe I3I holds pointer I23 inits then position until moved by either arm I22 or R26. Said pointer thus indicates the thendeparture from the set rate. Ihe chart I30 is continu ously rotated by clock-work or other suitable constant speed means, and the pointer I23 is provided with a suitable-stylus for recording its positlon on said chart. The amount and direction of departure from the setrate are thus continuously recorded.-

lit will be understood that the terms oscillating or oscillations as employed herein are not restricted to pivotal or rotary reverse movement rotating reversely with the spider element of the differential gearing might: constitute a rack member geared to the spider element so as to be reciprocated rectilinearly thereby within the limits defined by the contacts is and 2|.

It will also be apparent, for example, that-the resistance 44 or M of motor'3I or I8, may be either ohmic or reactive, and the employment of the term resistance is intended to include any other well-known form of impedance.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possiblewithi'n the scope of the invention claimed.

I claim: v

i. in a telemetric controller, means for cyclically transmitting signals of a function .of time corresponding with values of a variable, a motor, a second motor having a pair of shading coils one of which is continuously close circuited through a resistance and the other of which is connected to said transmitting means through a lower resistance for. causing said second motor to operate in reverse directions ineach of a pinrality of successive cycles under control of said signals and saidclose-circuited shading coil, contact means for controlling energization of the first motor, means actuated by the second motor for operating said contact means, said operating means including an element movable to effect closing of said contact means and adapted to continue its movement within limits beyond the point at'which it effects closing of said contact means, means operated by the first motor for shifting said element to a position wherein said contact means is opened, and means providing slippage between the first motor and said element when said element reaches either of said limits.

2. In a telemetric controller, motor means, means for cyclically transmitting impulses of a function of time corresponding with values of a variable, contact means for controlling energization of said motor means, oscillating means responsive to said impulses for operating a portion of said contact means in a positive direction during said impulses and in a negative direction during cessation of said impulses and for closing said contact means upon a predetermined algebraic accumulation of the differences in amplitude of said positive and negative oscillations of said contact means portion from a given reference point, said oscillating means comprising an element movable to effect closing of said contact means and adapted to continue its movement within limits beyond the point at which it effects closing of said contact means, and yielding means enabling said oscillating means to operate without actuating said element when said element reaches either of said limits.

3. In a telemetric control method, the steps comprising producing in each of a series of uniform time periods two'diiferent electrical circuit conditions, the duration of one condition being commensurate with the-actual value of a variable and the duration ofthe other condition being the complement of the one, oscillating an element in each of said time periods through an extent in a positive direction corresponding to the duration of one of said conditions and in a negative direction through an extent corresponding to the remaining portion of said period, and energizing a power means whenever the algebraic summation of the differences in amplitude of said positive and negative oscillations of said oscillating. .element exceeds a predetermined amount beyond a given reference point.

4. In a telemetric controller, means for transmitting in uniform time periods a signal of a duration corresponding with the value of a variable, pilot means operable in a positive direction in each period while said signal is on and in a negative direction during the remainder of each period, motor means, and motor controlling means operable in reverse directions by said pilot means for energizing said motor means upon a given algebraic accumulation of the difierences in amplitude of said positive and negative oscillations of said motor controlling means in either direction beyond a given reference point.

5. In a telemetric controller, motor means, means for cyclically transmitting impulses of a function of time corresponding with values of a 15 variable, contact means for controlling energization of said motor means in one direction or the other, said contact means including spaced contacts and a member movable with respect to said contacts, oscillating means responsive to said impulses for operating said member in one direc tion during said impulses and in the opposite direction during cessation of said impulses in each cycle and effecting engagement of said member with one or the other of said contacts as a result of an algebraic accumulation of the dilierences in the movements of said member in opposite directions during each cycle.

ED s. SMITH, JR. 

